Discriminator



July 1', 1958 P. H. SAVET 2,841,721

. DISCRIMINATOR Original Filed Feb. 1a. 1953 25 D i 1 I Q I I lN-PHASEREFERENCE VOLTAGE I I l u ...1 'Hm-Phms: OUTPUT fi I0 I j IN'PUT |2\ TRE T QUAD'RA u ou PUT 1 26 i QUAD'RATURE REFERENCE I K VOLTAGE v I I JINVENTOR. PAUL H- SAVET mmw;

ATTOPNEK DISCRIMINATOR Paul H. Savet, Westbury, N. Y., assignor toAmerican Bosch Anna Corporation, a corporation of New York Continuationof application Serial No. 337,483, February 1213, 1953. This applicationOctober 2, 1956, Serial No. 6 3,544

2 Claims. (Cl. 307149) The present invention relates to discriminatorsfor separating the inphase and quadrature components of a signal voltageand has particular reference to a circuit using a single high gainamplifier with auxiliary phasesensitive circuits to accomplish thisresult.

This application is a continuation of my application Serial Number337,483 filed February 18, 1953, now abandoned.

In a preferred embodiment of the present invention the output signal ofa thermal unit, sensitive only to inphase voltage, and the output signalof a second thermal unit, sensitive only to quadrature voltage, are fedback degeneratively with the signal voltage to the input of a high gainamplifier, the output of which is applied to both thermal units. By thisdevice, the output of one thermal unit is substantially the inphasecomponent of the signal, and the output of the other thermal unit issubstantially the quadrature component of the signal.

For a better understanding of the invention, reference nited StatesPatent ice 2,841,721 Patented July 1, 1958 27 in unit 19 is of 90 phase,i. e., is in quadrature with may be had to the accompanying diagrams, inwhich the 7 drawing is a schematic circuit diagram of the preferredembodiment of the invention.

In the drawing the signal voltage having both inphase and quadraturecomponents is supplied to terminals 10, while the inphase component ismade available at terminals 11 and the quadrature component is madeavailable at terminals 12. Terminals 10, 11, and 12 are connected inseries with the input terminals 13 of high gain amplifier 14, the outputterminals 15 of which are connected to the signal input terminals 16 and17 of the phase sensitive devices 18 and 19.

The phase sensitive devices 18 and 19 are preferably, but not limitedto, thermal units of the type fully disclosed in copending U. S. patentapplication Serial Number 242,957, filed August 21, 1951 for CircuitCoupling Device in the name of Joseph Statsinger and assigned to theassignee of this invention but will be briefly discussed here forcompleteness.

The thermal unit 18 comprises the pair of low coefiicient of temperatureresistors 20, 20 thermally coupled to a pair of high temperaturecoefficient 21, 21, each pair of resistors 20, 2t) and 21, 21 beingconnected in series and energized by the respective secondary windings22 and 23 of transformer 24. The signal input terminals 16 of unit 18are connected to the center tap 22a of winding 22 and the junction ofthe resistor pairs .20, 20, while the output of the unit is takenbetween the junction of resistors 21, 21 and the center tap 23a ofsecondary winding 23. In a unit of this type, the component of an inputsignal which is inphase with the reference voltage energizing theprimary winding 25 of the transformer 24 causes difierential heating ofthe resistors 20, 20 which reflected to the resistors 21, 21 produces avoltage proportional in magnitude to the inphase component of the inputsignal at the output of the unit. It should be noted that a component ofthe input voltage in quadrature with the reference voltage produces nodifferential heating of the voltage at primary winding 25, then thevoltage at terminals 11 will be an inphase voltage, while the voltage atterminals 12 is a quadrature voltage.

It will be shown, using the symbols listed below, that for theconditions of the drawing the output at terminals 11 is substantiallythe inphase component of the input voltage at terminals 10, and theoutput at terminals 12 is substantially the quadrature component of thevoltage at terminals 10.

I=R+jQ=input at terminals 10 A=voltage at terminals 11 jB=voltage atterminals 12 C=voltage input of amplifier 14 D=voltage output ofamplifier 14 K =gain of thermal unit 18 K =gain of thermal unit 19G=gain of amplifier 14 Now,

Therefore A =K G(R--A) And A R(K G) (KIG) If K G is large compared tounity, then A is substantially equal to R, and the voltage at terminals11 is substantially equal to the real part of the input signal, I.

Similarly jB=K (imaginary part of D) K G (imaginary part of C) So that i=J'(Q- 2 And If K G is large compared to unity, then 'B is substantiallyequal to jQ and the voltage at terminals 12 is substantially equal tothe quadrature component of the input signal I.

In order to make the factors K G and K G large with respect to unity,the amplifier 14 is chosen to have a high gain since the gain K and Kthrough the units 18 and 19 is usually small.

It can be seen that the present invention offers a simple method fordiscrimination of inphase and quadrature components from a signal sourceusing only one amplifier. The signal input to the amplifier is small sothat there is little danger of saturating the amplifier.

Although the invention has been shown and described as using thermalunits 18 and 19 for separating the in phase and quadrature components,the invention is not to be limited thereby, but other types of circuitsfor a similar purpose may be used, such as demodulatormodulator devices,for example.

I claim:

1. In a device of the character described, an electrical signal sourceproducing an electrical signal containing an inphase component and aquadrature component, an amplifier having an input and an output, afirst pair of series connected heating resistors and a first pair ofseries connected" heated resistors in close thermal contact butelectrically isolated from each other, a source of inphase referencevoltages connected to energize each of said first pairs of resistorsequally; a second pair of series connected heating resistors and asecondpair of series connected heated resistors inyclose thermal contact butelec-- trically isolated from each 'other, a source of quadrature phasereference voltages connected to energize equally 2. In a device of thecharacter described, an electrical signal source producing an electricalsignal containing an inphase component and a quadrature component, anamplifier having an input and an output, a first pairof series connectedheating resistors and a first pair of series connected heated resistorsin close thermal contact but electrically isolated from each other, asource of inphase reference voltages connectedxto energize each of saidfirst pairs of resistors equally, a second pair of series connectedheating resistors and a second pair of series connected heated resistorsin; close thermal contact but electrically isolated from each other, asource of quadrature phase reference voltages connected to energizeequally each: of said. second pairs of heating resistors, electricalconnections between the output of said amplifier and said first andsecond pairs of heating resistors whereby the heating resistors areunbalanced according to a portion of said amplifier output fordifferentially heating said resistors, electrical connections betweenthe input ofsaid amplifier, said electrical signal source and each ofsaid first and second pairs of heated resistors.

No references cited.

